llvm/tools/llvm-link/llvm-link.cpp

   1 //===- llvm-link.cpp - Low-level LLVM linker ------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This utility may be invoked in the following manner:
  10 //  llvm-link a.bc b.bc c.bc -o x.bc
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/ADT/STLExtras.h"
  15 #include "llvm/BinaryFormat/Magic.h"
  16 #include "llvm/Bitcode/BitcodeReader.h"
  17 #include "llvm/Bitcode/BitcodeWriter.h"
  18 #include "llvm/IR/AutoUpgrade.h"
  19 #include "llvm/IR/DiagnosticInfo.h"
  20 #include "llvm/IR/DiagnosticPrinter.h"
  21 #include "llvm/IR/LLVMContext.h"
  22 #include "llvm/IR/Module.h"
  23 #include "llvm/IR/ModuleSummaryIndex.h"
  24 #include "llvm/IR/Verifier.h"
  25 #include "llvm/IRReader/IRReader.h"
  26 #include "llvm/Linker/Linker.h"
  27 #include "llvm/Object/Archive.h"
  28 #include "llvm/Support/CommandLine.h"
  29 #include "llvm/Support/FileSystem.h"
  30 #include "llvm/Support/InitLLVM.h"
  31 #include "llvm/Support/Path.h"
  32 #include "llvm/Support/SourceMgr.h"
  33 #include "llvm/Support/SystemUtils.h"
  34 #include "llvm/Support/ToolOutputFile.h"
  35 #include "llvm/Support/WithColor.h"
  36 #include "llvm/Transforms/IPO/FunctionImport.h"
  37 #include "llvm/Transforms/IPO/Internalize.h"
  38 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
  39
  40 #include <memory>
  41 #include <utility>
  42 using namespace llvm;
  43
  44 static cl::OptionCategory LinkCategory("Link Options");
  45
  46 static cl::list<std::string> InputFilenames(cl::Positional, cl::OneOrMore,
  47                                             cl::desc("<input bitcode files>"),
  48                                             cl::cat(LinkCategory));
  49
  50 static cl::list<std::string> OverridingInputs(
  51     "override", cl::value_desc("filename"),
  52     cl::desc(
  53         "input bitcode file which can override previously defined symbol(s)"),
  54     cl::cat(LinkCategory));
  55
  56 // Option to simulate function importing for testing. This enables using
  57 // llvm-link to simulate ThinLTO backend processes.
  58 static cl::list<std::string> Imports(
  59     "import", cl::value_desc("function:filename"),
  60     cl::desc("Pair of function name and filename, where function should be "
  61              "imported from bitcode in filename"),
  62     cl::cat(LinkCategory));
  63
  64 // Option to support testing of function importing. The module summary
  65 // must be specified in the case were we request imports via the -import
  66 // option, as well as when compiling any module with functions that may be
  67 // exported (imported by a different llvm-link -import invocation), to ensure
  68 // consistent promotion and renaming of locals.
  69 static cl::opt<std::string>
  70     SummaryIndex("summary-index", cl::desc("Module summary index filename"),
  71                  cl::init(""), cl::value_desc("filename"),
  72                  cl::cat(LinkCategory));
  73
  74 static cl::opt<std::string>
  75     OutputFilename("o", cl::desc("Override output filename"), cl::init("-"),
  76                    cl::value_desc("filename"), cl::cat(LinkCategory));
  77
  78 static cl::opt<bool> Internalize("internalize",
  79                                  cl::desc("Internalize linked symbols"),
  80                                  cl::cat(LinkCategory));
  81
  82 static cl::opt<bool>
  83     DisableDITypeMap("disable-debug-info-type-map",
  84                      cl::desc("Don't use a uniquing type map for debug info"),
  85                      cl::cat(LinkCategory));
  86
  87 static cl::opt<bool> OnlyNeeded("only-needed",
  88                                 cl::desc("Link only needed symbols"),
  89                                 cl::cat(LinkCategory));
  90
  91 static cl::opt<bool> Force("f", cl::desc("Enable binary output on terminals"),
  92                            cl::cat(LinkCategory));
  93
  94 static cl::opt<bool> DisableLazyLoad("disable-lazy-loading",
  95                                      cl::desc("Disable lazy module loading"),
  96                                      cl::cat(LinkCategory));
  97
  98 static cl::opt<bool> OutputAssembly("S",
  99                                     cl::desc("Write output as LLVM assembly"),
 100                                     cl::Hidden, cl::cat(LinkCategory));
 101
 102 static cl::opt<bool> Verbose("v",
 103                              cl::desc("Print information about actions taken"),
 104                              cl::cat(LinkCategory));
 105
 106 static cl::opt<bool> DumpAsm("d", cl::desc("Print assembly as linked"),
 107                              cl::Hidden, cl::cat(LinkCategory));
 108
 109 static cl::opt<bool> SuppressWarnings("suppress-warnings",
 110                                       cl::desc("Suppress all linking warnings"),
 111                                       cl::init(false), cl::cat(LinkCategory));
 112
 113 static cl::opt<bool> PreserveBitcodeUseListOrder(
 114     "preserve-bc-uselistorder",
 115     cl::desc("Preserve use-list order when writing LLVM bitcode."),
 116     cl::init(true), cl::Hidden, cl::cat(LinkCategory));
 117
 118 static cl::opt<bool> PreserveAssemblyUseListOrder(
 119     "preserve-ll-uselistorder",
 120     cl::desc("Preserve use-list order when writing LLVM assembly."),
 121     cl::init(false), cl::Hidden, cl::cat(LinkCategory));
 122
 123 static cl::opt<bool> NoVerify("disable-verify",
 124                               cl::desc("Do not run the verifier"), cl::Hidden,
 125                               cl::cat(LinkCategory));
 126
 127 static cl::opt<bool> IgnoreNonBitcode(
 128     "ignore-non-bitcode",
 129     cl::desc("Do not report an error for non-bitcode files in archives"),
 130     cl::Hidden);
 131
 132 static cl::opt<bool> TryUseNewDbgInfoFormat(
 133     "try-experimental-debuginfo-iterators",
 134     cl::desc("Enable debuginfo iterator positions, if they're built in"),
 135     cl::init(false));
 136
 137 extern cl::opt<bool> UseNewDbgInfoFormat;
 138 extern cl::opt<cl::boolOrDefault> PreserveInputDbgFormat;
 139 extern cl::opt<bool> WriteNewDbgInfoFormat;
 140 extern bool WriteNewDbgInfoFormatToBitcode;
 141
 142 extern cl::opt<cl::boolOrDefault> LoadBitcodeIntoNewDbgInfoFormat;
 143
 144 static ExitOnError ExitOnErr;
 145
 146 // Read the specified bitcode file in and return it. This routine searches the
 147 // link path for the specified file to try to find it...
 148 //
 149 static std::unique_ptr<Module> loadFile(const char *argv0,
 150                                         std::unique_ptr<MemoryBuffer> Buffer,
 151                                         LLVMContext &Context,
 152                                         bool MaterializeMetadata = true) {
 153   SMDiagnostic Err;
 154   if (Verbose)
 155     errs() << "Loading '" << Buffer->getBufferIdentifier() << "'\n";
 156   std::unique_ptr<Module> Result;
 157   if (DisableLazyLoad)
 158     Result = parseIR(*Buffer, Err, Context);
 159   else
 160     Result =
 161         getLazyIRModule(std::move(Buffer), Err, Context, !MaterializeMetadata);
 162
 163   if (!Result) {
 164     Err.print(argv0, errs());
 165     return nullptr;
 166   }
 167
 168   if (MaterializeMetadata) {
 169     ExitOnErr(Result->materializeMetadata());
 170     UpgradeDebugInfo(*Result);
 171   }
 172
 173   return Result;
 174 }
 175
 176 static std::unique_ptr<Module> loadArFile(const char *Argv0,
 177                                           std::unique_ptr<MemoryBuffer> Buffer,
 178                                           LLVMContext &Context) {
 179   std::unique_ptr<Module> Result(new Module("ArchiveModule", Context));
 180   StringRef ArchiveName = Buffer->getBufferIdentifier();
 181   if (Verbose)
 182     errs() << "Reading library archive file '" << ArchiveName
 183            << "' to memory\n";
 184   Expected<std::unique_ptr<object::Archive>> ArchiveOrError =
 185       object::Archive::create(Buffer->getMemBufferRef());
 186   if (!ArchiveOrError)
 187     ExitOnErr(ArchiveOrError.takeError());
 188
 189   std::unique_ptr<object::Archive> Archive = std::move(ArchiveOrError.get());
 190
 191   Linker L(*Result);
 192   Error Err = Error::success();
 193   for (const object::Archive::Child &C : Archive->children(Err)) {
 194     Expected<StringRef> Ename = C.getName();
 195     if (Error E = Ename.takeError()) {
 196       errs() << Argv0 << ": ";
 197       WithColor::error() << " failed to read name of archive member"
 198                          << ArchiveName << "'\n";
 199       return nullptr;
 200     }
 201     std::string ChildName = Ename.get().str();
 202     if (Verbose)
 203       errs() << "Parsing member '" << ChildName
 204              << "' of archive library to module.\n";
 205     SMDiagnostic ParseErr;
 206     Expected<MemoryBufferRef> MemBuf = C.getMemoryBufferRef();
 207     if (Error E = MemBuf.takeError()) {
 208       errs() << Argv0 << ": ";
 209       WithColor::error() << " loading memory for member '" << ChildName
 210                          << "' of archive library failed'" << ArchiveName
 211                          << "'\n";
 212       return nullptr;
 213     };
 214
 215     if (!isBitcode(reinterpret_cast<const unsigned char *>(
 216                        MemBuf.get().getBufferStart()),
 217                    reinterpret_cast<const unsigned char *>(
 218                        MemBuf.get().getBufferEnd()))) {
 219       if (IgnoreNonBitcode)
 220         continue;
 221       errs() << Argv0 << ": ";
 222       WithColor::error() << "  member of archive is not a bitcode file: '"
 223                          << ChildName << "'\n";
 224       return nullptr;
 225     }
 226
 227     std::unique_ptr<Module> M;
 228     if (DisableLazyLoad)
 229       M = parseIR(MemBuf.get(), ParseErr, Context);
 230     else
 231       M = getLazyIRModule(MemoryBuffer::getMemBuffer(MemBuf.get(), false),
 232                           ParseErr, Context);
 233
 234     if (!M) {
 235       errs() << Argv0 << ": ";
 236       WithColor::error() << " parsing member '" << ChildName
 237                          << "' of archive library failed'" << ArchiveName
 238                          << "'\n";
 239       return nullptr;
 240     }
 241     if (Verbose)
 242       errs() << "Linking member '" << ChildName << "' of archive library.\n";
 243     if (L.linkInModule(std::move(M)))
 244       return nullptr;
 245   } // end for each child
 246   ExitOnErr(std::move(Err));
 247   return Result;
 248 }
 249
 250 namespace {
 251
 252 /// Helper to load on demand a Module from file and cache it for subsequent
 253 /// queries during function importing.
 254 class ModuleLazyLoaderCache {
 255   /// Cache of lazily loaded module for import.
 256   StringMap<std::unique_ptr<Module>> ModuleMap;
 257
 258   /// Retrieve a Module from the cache or lazily load it on demand.
 259   std::function<std::unique_ptr<Module>(const char *argv0,
 260                                         const std::string &FileName)>
 261       createLazyModule;
 262
 263 public:
 264   /// Create the loader, Module will be initialized in \p Context.
 265   ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>(
 266                             const char *argv0, const std::string &FileName)>
 267                             createLazyModule)
 268       : createLazyModule(std::move(createLazyModule)) {}
 269
 270   /// Retrieve a Module from the cache or lazily load it on demand.
 271   Module &operator()(const char *argv0, const std::string &FileName);
 272
 273   std::unique_ptr<Module> takeModule(const std::string &FileName) {
 274     auto I = ModuleMap.find(FileName);
 275     assert(I != ModuleMap.end());
 276     std::unique_ptr<Module> Ret = std::move(I->second);
 277     ModuleMap.erase(I);
 278     return Ret;
 279   }
 280 };
 281
 282 // Get a Module for \p FileName from the cache, or load it lazily.
 283 Module &ModuleLazyLoaderCache::operator()(const char *argv0,
 284                                           const std::string &Identifier) {
 285   auto &Module = ModuleMap[Identifier];
 286   if (!Module) {
 287     Module = createLazyModule(argv0, Identifier);
 288     assert(Module && "Failed to create lazy module!");
 289   }
 290   return *Module;
 291 }
 292 } // anonymous namespace
 293
 294 namespace {
 295 struct LLVMLinkDiagnosticHandler : public DiagnosticHandler {
 296   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 297     unsigned Severity = DI.getSeverity();
 298     switch (Severity) {
 299     case DS_Error:
 300       WithColor::error();
 301       break;
 302     case DS_Warning:
 303       if (SuppressWarnings)
 304         return true;
 305       WithColor::warning();
 306       break;
 307     case DS_Remark:
 308     case DS_Note:
 309       llvm_unreachable("Only expecting warnings and errors");
 310     }
 311
 312     DiagnosticPrinterRawOStream DP(errs());
 313     DI.print(DP);
 314     errs() << '\n';
 315     return true;
 316   }
 317 };
 318 } // namespace
 319
 320 /// Import any functions requested via the -import option.
 321 static bool importFunctions(const char *argv0, Module &DestModule) {
 322   if (SummaryIndex.empty())
 323     return true;
 324   std::unique_ptr<ModuleSummaryIndex> Index =
 325       ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 326
 327   // Map of Module -> List of globals to import from the Module
 328   FunctionImporter::ImportIDTable ImportIDs;
 329   FunctionImporter::ImportMapTy ImportList(ImportIDs);
 330
 331   auto ModuleLoader = [&DestModule](const char *argv0,
 332                                     const std::string &Identifier) {
 333     std::unique_ptr<MemoryBuffer> Buffer = ExitOnErr(errorOrToExpected(
 334         MemoryBuffer::getFileOrSTDIN(Identifier, /*IsText=*/true)));
 335     return loadFile(argv0, std::move(Buffer), DestModule.getContext(), false);
 336   };
 337
 338   ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader);
 339   // Owns the filename strings used to key into the ImportList. Normally this is
 340   // constructed from the index and the strings are owned by the index, however,
 341   // since we are synthesizing this data structure from options we need a cache
 342   // to own those strings.
 343   StringSet<> FileNameStringCache;
 344   for (const auto &Import : Imports) {
 345     // Identify the requested function and its bitcode source file.
 346     size_t Idx = Import.find(':');
 347     if (Idx == std::string::npos) {
 348       errs() << "Import parameter bad format: " << Import << "\n";
 349       return false;
 350     }
 351     std::string FunctionName = Import.substr(0, Idx);
 352     std::string FileName = Import.substr(Idx + 1, std::string::npos);
 353
 354     // Load the specified source module.
 355     auto &SrcModule = ModuleLoaderCache(argv0, FileName);
 356
 357     if (!NoVerify && verifyModule(SrcModule, &errs())) {
 358       errs() << argv0 << ": " << FileName;
 359       WithColor::error() << "input module is broken!\n";
 360       return false;
 361     }
 362
 363     Function *F = SrcModule.getFunction(FunctionName);
 364     if (!F) {
 365       errs() << "Ignoring import request for non-existent function "
 366              << FunctionName << " from " << FileName << "\n";
 367       continue;
 368     }
 369     // We cannot import weak_any functions without possibly affecting the
 370     // order they are seen and selected by the linker, changing program
 371     // semantics.
 372     if (F->hasWeakAnyLinkage()) {
 373       errs() << "Ignoring import request for weak-any function " << FunctionName
 374              << " from " << FileName << "\n";
 375       continue;
 376     }
 377
 378     if (Verbose)
 379       errs() << "Importing " << FunctionName << " from " << FileName << "\n";
 380
 381     // `-import` specifies the `<filename,function-name>` pairs to import as
 382     // definition, so make the import type definition directly.
 383     // FIXME: A follow-up patch should add test coverage for import declaration
 384     // in `llvm-link` CLI (e.g., by introducing a new command line option).
 385     ImportList.addDefinition(
 386         FileNameStringCache.insert(FileName).first->getKey(), F->getGUID());
 387   }
 388   auto CachedModuleLoader = [&](StringRef Identifier) {
 389     return ModuleLoaderCache.takeModule(std::string(Identifier));
 390   };
 391   FunctionImporter Importer(*Index, CachedModuleLoader,
 392                             /*ClearDSOLocalOnDeclarations=*/false);
 393   ExitOnErr(Importer.importFunctions(DestModule, ImportList));
 394
 395   return true;
 396 }
 397
 398 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
 399                       const cl::list<std::string> &Files, unsigned Flags) {
 400   // Filter out flags that don't apply to the first file we load.
 401   unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc;
 402   // Similar to some flags, internalization doesn't apply to the first file.
 403   bool InternalizeLinkedSymbols = false;
 404   for (const auto &File : Files) {
 405     auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(File, /*IsText=*/true);
 406
 407     // When we encounter a missing file, make sure we expose its name.
 408     if (auto EC = BufferOrErr.getError())
 409       if (EC == std::errc::no_such_file_or_directory)
 410         ExitOnErr(createStringError(EC, "No such file or directory: '%s'",
 411                                     File.c_str()));
 412
 413     std::unique_ptr<MemoryBuffer> Buffer =
 414         ExitOnErr(errorOrToExpected(std::move(BufferOrErr)));
 415
 416     std::unique_ptr<Module> M =
 417         identify_magic(Buffer->getBuffer()) == file_magic::archive
 418             ? loadArFile(argv0, std::move(Buffer), Context)
 419             : loadFile(argv0, std::move(Buffer), Context);
 420     if (!M) {
 421       errs() << argv0 << ": ";
 422       WithColor::error() << " loading file '" << File << "'\n";
 423       return false;
 424     }
 425
 426     // Note that when ODR merging types cannot verify input files in here When
 427     // doing that debug metadata in the src module might already be pointing to
 428     // the destination.
 429     if (DisableDITypeMap && !NoVerify && verifyModule(*M, &errs())) {
 430       errs() << argv0 << ": " << File << ": ";
 431       WithColor::error() << "input module is broken!\n";
 432       return false;
 433     }
 434
 435     // If a module summary index is supplied, load it so linkInModule can treat
 436     // local functions/variables as exported and promote if necessary.
 437     if (!SummaryIndex.empty()) {
 438       std::unique_ptr<ModuleSummaryIndex> Index =
 439           ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 440
 441       // Conservatively mark all internal values as promoted, since this tool
 442       // does not do the ThinLink that would normally determine what values to
 443       // promote.
 444       for (auto &I : *Index) {
 445         for (auto &S : I.second.SummaryList) {
 446           if (GlobalValue::isLocalLinkage(S->linkage()))
 447             S->setLinkage(GlobalValue::ExternalLinkage);
 448         }
 449       }
 450
 451       // Promotion
 452       if (renameModuleForThinLTO(*M, *Index,
 453                                  /*ClearDSOLocalOnDeclarations=*/false))
 454         return true;
 455     }
 456
 457     if (Verbose)
 458       errs() << "Linking in '" << File << "'\n";
 459
 460     bool Err = false;
 461     if (InternalizeLinkedSymbols) {
 462       Err = L.linkInModule(
 463           std::move(M), ApplicableFlags, [](Module &M, const StringSet<> &GVS) {
 464             internalizeModule(M, [&GVS](const GlobalValue &GV) {
 465               return !GV.hasName() || (GVS.count(GV.getName()) == 0);
 466             });
 467           });
 468     } else {
 469       Err = L.linkInModule(std::move(M), ApplicableFlags);
 470     }
 471
 472     if (Err)
 473       return false;
 474
 475     // Internalization applies to linking of subsequent files.
 476     InternalizeLinkedSymbols = Internalize;
 477
 478     // All linker flags apply to linking of subsequent files.
 479     ApplicableFlags = Flags;
 480   }
 481
 482   return true;
 483 }
 484
 485 int main(int argc, char **argv) {
 486   InitLLVM X(argc, argv);
 487   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
 488
 489   cl::HideUnrelatedOptions({&LinkCategory, &getColorCategory()});
 490   cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
 491
 492   // Load bitcode into the new debug info format by default.
 493   if (LoadBitcodeIntoNewDbgInfoFormat == cl::boolOrDefault::BOU_UNSET)
 494     LoadBitcodeIntoNewDbgInfoFormat = cl::boolOrDefault::BOU_TRUE;
 495
 496   // Since llvm-link collects multiple IR modules together, for simplicity's
 497   // sake we disable the "PreserveInputDbgFormat" flag to enforce a single
 498   // debug info format.
 499   PreserveInputDbgFormat = cl::boolOrDefault::BOU_FALSE;
 500
 501   LLVMContext Context;
 502   Context.setDiagnosticHandler(std::make_unique<LLVMLinkDiagnosticHandler>(),
 503                                true);
 504
 505   if (!DisableDITypeMap)
 506     Context.enableDebugTypeODRUniquing();
 507
 508   auto Composite = std::make_unique<Module>("llvm-link", Context);
 509   Linker L(*Composite);
 510
 511   unsigned Flags = Linker::Flags::None;
 512   if (OnlyNeeded)
 513     Flags |= Linker::Flags::LinkOnlyNeeded;
 514
 515   // First add all the regular input files
 516   if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
 517     return 1;
 518
 519   // Next the -override ones.
 520   if (!linkFiles(argv[0], Context, L, OverridingInputs,
 521                  Flags | Linker::Flags::OverrideFromSrc))
 522     return 1;
 523
 524   // Import any functions requested via -import
 525   if (!importFunctions(argv[0], *Composite))
 526     return 1;
 527
 528   if (DumpAsm)
 529     errs() << "Here's the assembly:\n" << *Composite;
 530
 531   std::error_code EC;
 532   ToolOutputFile Out(OutputFilename, EC,
 533                      OutputAssembly ? sys::fs::OF_TextWithCRLF
 534                                     : sys::fs::OF_None);
 535   if (EC) {
 536     WithColor::error() << EC.message() << '\n';
 537     return 1;
 538   }
 539
 540   if (!NoVerify && verifyModule(*Composite, &errs())) {
 541     errs() << argv[0] << ": ";
 542     WithColor::error() << "linked module is broken!\n";
 543     return 1;
 544   }
 545
 546   if (Verbose)
 547     errs() << "Writing bitcode...\n";
 548   auto SetFormat = [&](bool NewFormat) {
 549     Composite->setIsNewDbgInfoFormat(NewFormat);
 550     if (NewFormat)
 551       Composite->removeDebugIntrinsicDeclarations();
 552   };
 553   if (OutputAssembly) {
 554     SetFormat(WriteNewDbgInfoFormat);
 555     Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
 556   } else if (Force || !CheckBitcodeOutputToConsole(Out.os())) {
 557     SetFormat(UseNewDbgInfoFormat && WriteNewDbgInfoFormatToBitcode);
 558     WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder);
 559   }
 560
 561   // Declare success.
 562   Out.keep();
 563
 564   return 0;
 565 }